The present invention relates to liquid crystal displays and, more particularly, to a novel dichroic liquid crystal display having a bright background and dark characters in the unactivated state of the parallel-nematic mode.
Known dichroic liquid crystal displays, i.e. a display in which the liquid crystal material is host to a guest dichroic dye, apparently operate best in the parallel-nematic configuration, wherein the elongated axes, or directors of both the liquid crystal molecules and their guest, light-absorbing dichroic dye molecules, are aligned in the same direction parallel to the wall of the display cell, in the electrically unexcited state. In this condition, the molecules absorb the majority of incident light, and render the background of the display, as well as any unactivated character segments, to a dark condition. Character segments are electrically excited to align the molecules perpendicular to the cell walls and achieve a less-absorbing state displaying relatively bright characters against the dark background. Thus, while the character segments can be energized between bright and dark conditions, the background areas are generally relatively dark, due to the parallel molecular alignment thereat and hitherto could only be placed in a bright condition by continual electrical activation of the background areas. Conditional electrical activation is not desirable from the viewpoint of cell fabrication cost and generation of an additional signal for such activation. Accordingly, a dichroic liquid crystal display operating in the parallel-nematic mode and having a relatively bright background upon which appear relatively dark characters, without electrical activation of background areas, is highly desirable.